Recently many people complained that they can’t see the iPhone screen when wearing a polarized sunglasses after replacing the China made iPhone screen and they thought the problems maybe lie in the China made screens quality. In order to figure out why exactly did this happen, we’ve collected some information to share with you to explain this issue briefly.
First we need to know the structure of the LCD screen and how it works!
As you can see from the picture above, each LCD screen contains backlight unit, rear polarizer (near to backlight unit), TFT array, liquid crystal, color filter and front polarizer (near to screen display).
What related mostly to our problem here is the polarizers, which is used to filter the lights and allows the light of specific direction to pass and effectively eliminate the extra glare and it plays an important role in display image quality and performance.
Speaking of the polarizing film, we need to know the working principle of the polarizer which allows just the specific direction lights to go through, thus you see only the polarized lights from your screen and it can’t be recognized by our naked eyes, which we can tell by wearing the polarizer sunglasses. When you put the 2 pieces of polarizer in perpendicular angle you can’t see any lights through. And when you wear the polarized sunglasses, that means you put another polarizer on, just like the pictures showed below, which explained why you can’t see the screen in specific angle.
This two polarizers here are just like you wearing the polarized sunglass to look at the screen. The front polarizer is equal to your polarized sunglasses, and the other polarizer is equal to the one in your phone (the one near the display), you can see the magic cube clearly when the 2 polarizers are parallel to each other, as the angle changed, the less lights can pass through, the magic cube seems to fade away, and when this 2 pieces of polarizer are perpendicular to each other, you can hardly see the magic tube.
Here we found some other cellphones also encountered this phenomenon.
Like Samsung galaxy S5, when you put it at 45°, the screen is all black, other angles are fine.
For MeiZu MX3, you can see it clearly in 90°,however when you put it horizontal, it gets black.
For our most concerned iPhones, the iPhone 5 and 5S, you can see it in all angles with no problem, except for the 5S screen are tending to be yellowish and reddish.
And for iPhone 6 series, there is only little discoloration on the screen.
As we know that Apple has improved the screen polarizer in iPhone 6 series which can be explained briefly with below picture, actually adding a quarter-wave plate within the screen can turn the linear polarized light into circular polarized light, so the lights can spread from multiple directions, thus you can see the screen in every angle.
Luckily, LCD display technology has been quietly evolved in recent years, more and more cellphones are tending to improve their screen technology, the polarizer issues can hardly be found in smart phones now.
For the China made iPhone screens, most of the factories have used third party polarized films instead of OEM one because of the cost. According to our research, you may experience this problem in nearly half of all China made iPhone screens. As it's summer time, more and more customers would wear sunglasses while using the phone. We suggest you to test all your screens before installation.